CiteULike: Group: cliamte_change - library [161 articles]

Detection of human influence on twentieth-century precipitation trends

Xuebin Zhang — 2007-07-25T20:16:18-00:00

Nature, Vol. 448, No. 7152. (26 July 2007), pp. 461-465.

Dietary fatty acids correlate with prostate cancer biopsy grade and volume in Jamaican men.

CR Ritch — 2007-02-11T16:29:11-00:00

J Urol, Vol. 177, No. 1. (January 2007)

PURPOSE: Jamaica has the highest incidence of prostate cancer in the world. Dietary fat is associated with prostate cancer. The Omega6 polyunsaturated fatty acids have been shown to stimulate prostate carcinogenesis and the Jamaican diet is rich in linoleic acid. We hypothesized positive correlations between Omega6 polyunsaturated fatty acid, prostate specific antigen and prostate biopsy pathology. MATERIALS AND METHODS: A total of 148 men were enrolled in Kingston, Jamaica. Serum prostate specific antigen and erythrocyte membrane polyunsaturated fatty acids were analyzed. Men with prostate specific antigen 2.6 ng/ml or greater underwent biopsy. Histopathological and statistical analyses were performed on available data. RESULTS: Of the 54 men who underwent biopsy 24 had prostate cancer, 17 had a Gleason score of 7 or greater and 11 had a tumor volume of 50% or greater. There were significant positive correlations between linoleic acid and Gleason score (p = 0.009), and the linoleic acid-to-docosahexaenoic acid (Omega3) ratio and tumor volume (p = 0.03). There was a significant negative correlation between the arachidonic acid (Omega6)-to-docosapentanoic acid (Omega3) ratio and Gleason score (p = 0.04). Statistical correlations between prostate specific antigen and polyunsaturated fatty acids were inconsistent. CONCLUSIONS: The positive correlations between linoleic acid and Gleason score, and the linoleic acid-to-docosahexaenoic acid ratio and tumor volume support studies showing that Omega6 polyunsaturated fatty acids stimulate and Omega3 polyunsaturated fatty acids inhibit prostate cancer growth. The negative correlation between the arachidonic acid-to-docosapentanoic acid ratio and Gleason score supports studies that demonstrate increased metabolism of arachidonic acid in prostate cancer to form carcinogenic metabolites, namely prostaglandin E2. Our findings support the association between dietary fatty acids and prostate cancer, and they warrant further dietary and tissue studies in high risk populations.

Lactoperoxidase: physico-chemical properties, occurrence, mechanism of action and applications

KD Kussendrager — 2007-03-27T20:17:21-00:00

Lactoperoxidase (LP) is one of the most prominent enzymes in bovine milk and catalyses the inactivation of a wide range of micro-organisms in the lactoperoxidase system (LP-s). LP-systems are also identified as natural antimicrobial systems in human secretions such as saliva, tear-fluid and milk and are found to be harmless to mammalian cells. The detailed molecular structure of LP is identified and the major products generated by the LP-s and their antimicrobial action have been elucidated for the greater part. In this paper several aspects of bovine LP and LP-s are discussed, including physico-chemical properties, occurrence in milk and colostrum and mechanisms of action. Since the introduction of industrial processes for the isolation of LP from milk and whey the interest in this enzyme has increased considerably and attention will be paid to potential and actual applications of LP-systems as biopreservatives in food and other products.

Impact of global dimming and brightening on global warming

Martin Wild — 2007-02-26T19:27:09-00:00

Geophysical Research Letters, Vol. 34 (20 February 2007), L04702.

Methane carbon isotope effects caused by atomic chlorine in the marine boundary layer: Global model results compared with Southern Hemisphere measurements

W Allan — 2007-02-26T19:24:54-00:00

Journal of Geophysical Research, Vol. 112 (22 February 2007), D04306.

Clues from MIS 11 to predict the future climate - a modelling point of view

MF Loutre — 2007-02-20T20:15:12-00:00

Earth and Planetary Science Letters, Vol. 212, No. 1-2. (15 July 2003), pp. 213-224.

Simulations performed with the LLN two-dimensional Northern Hemisphere climate model have confirmed that climate is largely triggered by changes in insolation forcing although atmospheric CO2 concentration also plays an important role, in particular in the amplitude of the simulated variations. Marine isotope stage 11 (MIS 11) some 400 kyr ago and the future share a common feature related to climate forcing, i.e. the insolation at these times displays small similar variations. MIS 11 can be considered an analogue for future natural climate changes. Different simulations were performed to identify the conditions constraining the length of the MIS 11 simulated interglacial. Clearly its length strongly depends on the phase relationship between insolation and CO2 variations. It is only when insolation and CO2 act together towards a cooling, i.e. they both decrease together, that the climate enters quickly into glaciation and that the interglacial may be short. Otherwise each forcing alone is not able to drive the system into glaciation and the climate remains in an interglacial state. The same situation applies for the future. However, we already know that CO2 and insolation do not play together. Indeed, insolation has been decreasing since 11 kyr BP and CO2 concentration remains above 260 ppmv, with a general increasing trend over the last 8000 yr. Therefore we conclude that the long interglacial simulated for the future is a robust feature and the Earth will not enter naturally into glaciation before 50 kyr AP.

Essential Fatty acids - a review.

UN Das — 2007-01-23T14:29:09-00:00

Curr Pharm Biotechnol, Vol. 7, No. 6. (December 2006), pp. 467-482.

Essential fatty acids (EFAs): cis-linoleic acid (LA) and alpha-linolenic acid (ALA) are essential for humans and their deficiency is rare in humans due to their easy availability in diet. EFAs are metabolized to their respective long-chain metabolites: dihomo-gamma-linolenic acid (DGLA), and arachidonic acid (AA) from LA; and eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from ALA. Some of these long-chain metabolites form precursors to respective prostaglandins (PGs), thromboxanes (TXs), and leukotrienes (LTs), lipoxins (LXs) and resolvins. EFAs and their metabolites may function as endogenous angiotensin converting enzyme and HMG-CoA reductase inhibitors, nitric oxide enhancers, anti-hypertensives, and anti-atherosclerotic molecules. EFAs react with nitric oxide (NO) to yield respective nitroalkene derivatives that have cell-signaling actions via ligation and activation of peroxisome proliferator-activated receptors (PPARs). In several diseases such as obesity, hypertension, diabetes mellitus, coronary heart disease, alcoholism, schizophrenia, Alzheimer's disease, atherosclerosis, and cancer the metabolism of EFAs is altered. Thus, EFAs and their derivatives have significant clinical implications.

Anthropogenic CO2 accumulation rates in the North Atlantic Ocean from changes in the 13C/12C of dissolved inorganic carbon

P Quay — 2007-02-12T18:26:33-00:00

Global Biogeochemical Cycles, Vol. 21 (9 February 2007), GB1009.

Inverse estimates of the oceanic sources and sinks of natural CO2 and the implied oceanic carbon transport

Mikaloff Fletcher — 2007-02-12T18:09:51-00:00

Global Biogeochemical Cycles, Vol. 21 (10 February 2007), GB1010.

Quantitative analysis of the benefits and risks of consuming farmed and wild salmon.

JA Foran — 2007-01-19T18:01:29-00:00

J Nutr, Vol. 135, No. 11. (November 2005), pp. 2639-2643.

Contaminants in farmed Atlantic and wild Pacific salmon raise important questions about the competing health benefits and risks of fish consumption. A benefit-risk analysis was conducted to compare quantitatively the cancer and noncancer risks of exposure to organic contaminants in salmon with the (n-3) fatty acid-associated health benefits of salmon consumption. Recommended levels of (n-3) fatty acid intake, as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), may be achieved by consuming farmed or wild salmon while maintaining an acceptable level of noncarcinogenic risk. However, the recommended level of EPA+DHA intake cannot be achieved solely from farmed or wild salmon while maintaining an acceptable level of carcinogenic risk. Although the benefit-risk ratio for carcinogens and noncarcinogens is significantly greater for wild Pacific salmon than for farmed Atlantic salmon as a group, the ratio for some subgroups of farmed salmon is on par with the ratio for wild salmon. This analysis suggests that risk of exposure to contaminants in farmed and wild salmon is partially offset by the fatty acid-associated health benefits. However, young children, women of child-bearing age, pregnant women, and nursing mothers not at significant risk for sudden cardiac death associated with CHD but concerned with health impairments such as reduction in IQ and other cognitive and behavioral effects, can minimize contaminant exposure by choosing the least contaminated wild salmon or by selecting other sources of (n-3) fatty acids.

Observation of glacial isostatic adjustment in “stable” North America with GPS

Giovanni Sella — 2007-01-30T20:06:47-00:00

Geophysical Research Letters, Vol. 34 (26 January 2007), L02306.

A new satellite retrieval method for precipitable water vapor over land and ocean

Merritt Deeter — 2007-01-30T20:05:49-00:00

Geophysical Research Letters, Vol. 34 (23 January 2007), L02815.

Influences of biomass heat and biochemical energy storages on the land surface fluxes and radiative temperature

Lianhong Gu — 2007-01-22T20:51:41-00:00

Journal of Geophysical Research, Vol. 112 (20 January 2007), D02107.

The fats of life: the role of omega-3 fatty acids in the prevention of coronary heart disease.

CR Harper — 2007-01-06T18:38:28-00:00

Arch Intern Med, Vol. 161, No. 18. (8 October 2001), pp. 2185-2192.

Epidemiological and clinical trial evidence suggests that omega-3 polyunsaturated fatty acids (PUFAs) might have a significant role in the prevention of coronary heart disease. Dietary sources of omega-3 PUFA include fish oils rich in eicosapentaenoic acid and docosahexaenoic acid along with plants rich in alpha-linolenic acid. Randomized clinical trials with fish oils (eicosapentaenoic acid and docosahexaenoic acid) and alpha-linolenic acid have demonstrated reductions in risk that compare favorably with those seen in landmark secondary prevention trials with lipid-lowering drugs. Several mechanisms explaining the cardioprotective effect of omega-3 PUFAs have been suggested, including antiarrhythmic, hypolipidemic, and antithrombotic roles. Although official US guidelines for the dietary intake of omega-3 PUFAs are not available, several international guidelines have been published. Fish is an important source of omega-3 PUFAs in the US diet; however, vegetable sources, including grains and oils, offer an alternative source for those who are unable to regularly consume fish.

The importance of the ratio of omega-6/omega-3 essential fatty acids.

AP Simopoulos — 2007-01-14T18:23:06-00:00

Biomed Pharmacother, Vol. 56, No. 8. (October 2002), pp. 365-379.

Several sources of information suggest that human beings evolved on a diet with a ratio of omega-6 to omega-3 essential fatty acids (EFA) of approximately 1 whereas in Western diets the ratio is 15/1-16.7/1. Western diets are deficient in omega-3 fatty acids, and have excessive amounts of omega-6 fatty acids compared with the diet on which human beings evolved and their genetic patterns were established. Excessive amounts of omega-6 polyunsaturated fatty acids (PUFA) and a very high omega-6/omega-3 ratio, as is found in today's Western diets, promote the pathogenesis of many diseases, including cardiovascular disease, cancer, and inflammatory and autoimmune diseases, whereas increased levels of omega-3 PUFA (a low omega-6/omega-3 ratio) exert suppressive effects. In the secondary prevention of cardiovascular disease, a ratio of 4/1 was associated with a 70% decrease in total mortality. A ratio of 2.5/1 reduced rectal cell proliferation in patients with colorectal cancer, whereas a ratio of 4/1 with the same amount of omega-3 PUFA had no effect. The lower omega-6/omega-3 ratio in women with breast cancer was associated with decreased risk. A ratio of 2-3/1 suppressed inflammation in patients with rheumatoid arthritis, and a ratio of 5/1 had a beneficial effect on patients with asthma, whereas a ratio of 10/1 had adverse consequences. These studies indicate that the optimal ratio may vary with the disease under consideration. This is consistent with the fact that chronic diseases are multigenic and multifactorial. Therefore, it is quite possible that the therapeutic dose of omega-3 fatty acids will depend on the degree of severity of disease resulting from the genetic predisposition. A lower ratio of omega-6/omega-3 fatty acids is more desirable in reducing the risk of many of the chronic diseases of high prevalence in Western societies, as well as in the developing countries, that are being exported to the rest of the world.

Physiology: Obesity and gut flora

Matej Bajzer — 2006-12-20T20:06:27-00:00

Nature, Vol. 444, No. 7122. (21 December 2006), pp. 1009-1010.

The Heartbeat of the Oligocene Climate System

Heiko Palike — 2007-01-15T21:26:56-00:00

Science, Vol. 314, No. 5807. (22 December 2006), pp. 1894-1898.

A 13-million-year continuous record of Oligocene climate from the equatorial Pacific reveals a pronounced "heartbeat" in the global carbon cycle and periodicity of glaciations. This heartbeat consists of 405,000-, 127,000-, and 96,000-year eccentricity cycles and 1.2-million-year obliquity cycles in periodically recurring glacial and carbon cycle events. That climate system response to intricate orbital variations suggests a fundamental interaction of the carbon cycle, solar forcing, and glacial events. Box modeling shows that the interaction of the carbon cycle and solar forcing modulates deep ocean acidity as well as the production and burial of global biomass. The pronounced 405,000-year eccentricity cycle is amplified by the long residence time of carbon in the oceans. 10.1126/science.1133822

n-3 fatty acids and cardiovascular disease.

JL Breslow — 2007-01-06T18:38:45-00:00

Am J Clin Nutr, Vol. 83, No. 6 Suppl. (June 2006)

The results of prospective cohort studies indicate that consuming fish or fish oil containing the n-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) is associated with decreased cardiovascular death, whereas consumption of the vegetable oil-derived n-3 fatty acid a-linolenic acid is not as effective. Randomized control trials (RCTs) in the context of secondary prevention also indicate that the consumption of EPA plus DHA is protective at doses <1 g/d. The therapeutic effect appears to be due to suppression of fatal arrhythmias rather than stabilization of atherosclerotic plaques. At doses >3 g/d, EPA plus DHA can improve cardiovascular disease risk factors, including decreasing plasma triacylglycerols, blood pressure, platelet aggregation, and inflammation, while improving vascular reactivity. Mainly on the basis of the results of RCTs, the American Heart Association recommends that everyone eat oily fish twice per week and that those with coronary heart disease eat 1 g/d of EPA plus DHA from oily fish or supplements. Directions for future research include (1) RCTs to confirm the initial trials showing that EPA plus DHA decreases cardiovascular death and additional studies to determine whether this effect is due to EPA, DHA, or the combination; the dosage of the effective components; and whether the mechanism of action in humans is prevention of fatal arrhythmias. (2) Clinical studies to determine whether the reduction in cardiovascular disease risk factors is due to EPA, DHA, or the combination and the dosage of the effective components. (3) Clinical studies to determine whether vegetable oil-derived alpha-linolenic acid added to a diet enriched in n-6 fatty acids can effectively substitute for fish oil-derived EPA plus DHA.

Effects of the 11-year solar cycle on the Earth atmosphere revealed in ECMWF reanalyses

YC Suh — 2007-01-05T15:01:28-00:00

Geophysical Research Letters, Vol. 33 (27 December 2006), L24705.

Observations of the impact of a major Saharan dust storm on the atmospheric radiation balance

A Slingo — 2007-01-05T14:42:11-00:00

Geophysical Research Letters, Vol. 33 (30 December 2006), L24817.

Impact of the Atlantic Multidecadal Oscillation on the Asian summer monsoon

Riyu Lu — 2007-01-05T14:35:51-00:00

Geophysical Research Letters, Vol. 33 (20 December 2006), L24701.

Misleading patterns in correlation maps

KT Coughlin — 2007-01-04T12:58:26-00:00

Journal of Geophysical Research, Vol. 111 (16 December 2006), D24102.

Effect of Fructose Overfeeding and Fish Oil Administration on Hepatic De Novo Lipogenesis and Insulin Sensitivity in Healthy Men

David Faeh — 2006-12-30T23:39:10-00:00

Diabetes, Vol. 54, No. 7. (1 July 2005), pp. 1907-1913.

High-fructose diet stimulates hepatic de novo lipogenesis (DNL) and causes hypertriglyceridemia and insulin resistance in rodents. Fructose-induced insulin resistance may be secondary to alterations of lipid metabolism. In contrast, fish oil supplementation decreases triglycerides and may improve insulin resistance. Therefore, we studied the effect of high-fructose diet and fish oil on DNL and VLDL triglycerides and their impact on insulin resistance. Seven normal men were studied on four occasions: after fish oil (7.2 g/day) for 28 days; a 6-day high-fructose diet (corresponding to an extra 25% of total calories); fish oil plus high-fructose diet; and control conditions. Following each condition, fasting fractional DNL and endogenous glucose production (EGP) were evaluated using [1-13C]sodium acetate and 6,6-2H2 glucose and a two-step hyperinsulinemic-euglycemic clamp was performed to assess insulin sensitivity. High-fructose diet significantly increased fasting glycemia (7 +/- 2%), triglycerides (79 +/- 22%), fractional DNL (sixfold), and EGP (14 +/- 3%, all P < 0.05). It also impaired insulin-induced suppression of adipose tissue lipolysis and EGP (P < 0.05) but had no effect on whole- body insulin-mediated glucose disposal. Fish oil significantly decreased triglycerides (37%, P < 0.05) after high-fructose diet compared with high-fructose diet without fish oil and tended to reduce DNL but had no other significant effect. In conclusion, high-fructose diet induced dyslipidemia and hepatic and adipose tissue insulin resistance. Fish oil reversed dyslipidemia but not insulin resistance.

DOCOSAHEXAENOIC ACID, FATTY ACID-INTERACTING PROTEINS, AND NEURONAL FUNCTION: Breastmilk and Fish Are Good for You

Joseph Marszalek1 — 2006-12-30T23:07:45-00:00

Annual Review of Cell and Developmental Biology, Vol. 21 (1 July 2005), pp. 633-657.

In contrast to other tissues, the nervous system is enriched in the polyunsaturated fatty acids (PUFAs): arachidonic acid (AA, 20:4 n-6) and docosahexaenoic acid (DHA, 22:6 n-3). Despite their abundance in the nervous system, AA and DHA cannot be synthesized de novo by mammals; they, or their precursors, must be ingested from dietary sources and transported to the brain. During late gestation and the early postnatal period, neurodevelopment is exceptionally rapid, and substantial amounts of PUFAs, especially DHA, are critical to ensure neurite outgrowth as well as proper brain and retina development. Here, we review the various functions of DHA in the nervous system, the proteins involved in its internalization and metabolism into phospholipids, and its relationship to several neurological disorders, including Alzheimer's disease and depression.

Hepatic de novo lipogenesis in normoinsulinemic and hyperinsulinemic subjects consuming high-fat, low-carbohydrate and low-fat, high-carbohydrate isoenergetic diets.

JM Schwarz — 2006-12-30T22:30:08-00:00

Am J Clin Nutr, Vol. 77, No. 1. (January 2003), pp. 43-50.

BACKGROUND: Hypertriglyceridemia is associated with increased risk of cardiovascular disease. Until recently, the importance of hepatic de novo lipogenesis (DNL) in contributing to hypertriglyceridemia was difficult to assess because of methodologic limitations. OBJECTIVE: We evaluated the extent of the contribution by DNL to different conditions associated with hypertriglyceridemia. DESIGN: After 5 d of an isoenergetic high-fat, low-carbohydrate diet, fasting DNL was measured in normoinsulinemic (<or= 85 pmol/L) lean (n = 9) and obese (n = 6) and hyperinsulinemic (>or= 115 pmol/L) obese (n = 8) subjects. Fasting DNL was measured after a low-fat, high-carbohydrate diet in normoinsulinemic lean (n = 5) and hyperinsulinemic obese (n = 5) subjects. Mass isotopomer distribution analysis was used to measure the fraction of newly synthesized fatty acids in VLDL-triacylglycerol. RESULTS: With the high-fat, low-carbohydrate diet, hyperinsulinemic obese subjects had a 3.7-5.3-fold higher fractional DNL (8.5 +/- 0.7%) than did normoinsulinemic lean (1.6 +/- 0.5%) or obese (2.3 +/- 0.3%) subjects. With the low-fat, high-carbohydrate diet, normoinsulinemic lean and hyperinsulinemic obese subjects had similarly high fractional DNL (13 +/- 5.1% and 12.8 +/- 1.4%, respectively). Compared with baseline, consumption of the high-fat, low-carbohydrate diet did not affect triacylglycerol concentrations. However, after the low-fat, high-carbohydrate diet, triacylglycerols increased significantly and DNL was 5-6-fold higher than in normoinsulinemic subjects consuming a high-fat diet. The increase in triacylglycerol after the low-fat, high-carbohydrate diet was correlated with fractional DNL (P < 0.01), indicating that subjects with high DNL had the greatest increase in triacylglycerols. CONCLUSIONS: These results support the concept that both hyperinsulinemia and a low-fat diet increase DNL, and that DNL contributes to hypertriglyceridemia.

Docosahexaneoic acid (22:6,n-3) regulates rat hepatocyte SREBP-1 nuclear abundance by Erk- and 26S proteasome-dependent pathways.

D Botolin — 2006-05-07T00:03:09-00:00

J Lipid Res, Vol. 47, No. 1. (January 2006), pp. 181-192.

Insulin induces and dietary n-3 PUFAs suppress hepatic de novo lipogenesis by controlling sterol-regulatory element binding protein-1 nuclear abundance (nSREBP-1). Our goal was to define the mechanisms involved in this regulatory process. Insulin treatment of rat primary hepatocytes rapidly augments nSREBP-1 and mRNA(SREBP-1c) while suppressing mRNA(Insig-2) but not mRNA(Insig-1). These events are preceded by rapid but transient increases in Akt and Erk phosphorylation. Removal of insulin from hepatocytes leads to a rapid decline in nSREBP-1 [half-time (T1/2) approximately 10 h] that is abrogated by inhibitors of 26S proteasomal degradation. 22:6,n-3, the major n-3 PUFA accumulating in livers of fish oil-fed rats, suppresses hepatocyte levels of nSREBP-1, mRNA(SREBP-1c), and mRNA(Insig-2) but modestly and transiently induces mRNA(Insig-1). More importantly, 22:6,n-3 accelerates the disappearance of hepatocyte nSREBP-1 (T1/2 approximately 4 h) through a 26S proteasome-dependent process. 22:6,n-3 has minimal effects on microsomal SREBP-1 and sterol-regulatory element binding protein cleavage-activating protein or nuclear SREBP-2. 22:6,n-3 transiently inhibits insulin-induced Akt phosphorylation but induces Erk phosphorylation. Inhibitors of Erk phosphorylation, but not overexpressed constitutively active Akt, rapidly attenuate 22:6,n-3 suppression of nSREBP-1. Thus, 22:6,n-3 suppresses hepatocyte nSREBP-1 through 26S proteasome- and Erk-dependent pathways. These studies reveal a novel mechanism for n-3 PUFA regulation of hepatocyte nSREBP-1 and lipid metabolism.

Chemopreventive effects of dietary flaxseed oil on colon tumor development.

C Dwivedi — 2006-01-09T02:08:55-00:00

Nutr Cancer, Vol. 51, No. 1. (2005), pp. 52-58.

Fatty acid composition of dietary fat, primarily the levels of omega-3 and omega-6 polyunsaturated fatty acids, has shown profound effect on colon tumor development in animal studies. Fats containing omega-6 fatty acids (for example, corn oil) enhanced and omega-3 fatty acids (for example, fish oil and mustard oil) reduced chemically induced colon tumors in rats. The purpose of this study was to investigate the effects of dietary flaxseed oil (containing alpha-linolenic acid, an omega-3 polyunsaturated fatty acid) on azoxymethane-induced colon tumor in rats and how it compared with the dietary corn oil-treated group. Male Fischer rats, separated into 2 groups of 30, were assigned to the AIN-93M diet, which was supplemented with either 15% corn oil or 15% flaxseed oil. Carcinogenesis was initiated with subcutaneous injections of azoxymethane (15 mg/kg) once a week for three consecutive weeks. Thirty-five weeks after initiation, the rats were sacrificed under ether anesthesia. Blood was collected by cardiac puncture. The gastrointestinal tract was isolated and flushed with ice-cold normal saline. The site, size, and number of tumors were recorded. The incidence and multiplicity of the tumors in the colon were determined. The fatty acid composition in the serum, colon, and tumors was estimated by using gas chromatography-flame ionization detection. Colon tumor incidence was found to be 100% and 54%, whereas multiplicity was found to be 3.1 and 0.7 tumors per rat in corn oil- and flaxseed oil-treated groups, respectively. Tumor size was significantly larger in the corn oil-treated group than in the flaxseed oil group. Colon and serum samples of the corn oil group showed an increase in the omega-6 fatty acid levels, whereas the flaxseed oil group exhibited an increase in the omega-3 fatty acid levels. The results indicate that dietary flaxseed oil, containing high levels of omega-3 fatty acids, is effective in preventing colon tumor development when compared with dietary corn oil containing omega-6 fatty acids in rats.

Omega-3 and omega-6 fatty acids stimulate cell membrane expansion by acting on syntaxin 3

Frã©dã©ric Darios — 2006-04-06T01:29:08-00:00

Nature, Vol. 440, No. 7085., pp. 813-817.

[Lipids, depression and suicide]

A Colin — 2006-12-29T18:39:18-00:00

Encephale, Vol. 29, No. 1. (b 2003), pp. 49-58.

Polyunsatured fatty acids are made out of a hydrocarbonated chain of variable length with several double bonds. The position of the first double bond (omega) differentiates polyunsatured omega 3 fatty acids (for example: alpha-linolenic acid or alpha-LNA) and polyunsatured omega 6 fatty acids (for example: linoleic acid or LA). These two classes of fatty acids are said to be essential because they cannot be synthetised by the organism and have to be taken from alimentation. The omega 3 are present in linseed oil, nuts, soya beans, wheat and cold water fish whereas omega 6 are present in maize, sunflower and sesame oil. Fatty acids are part of phospholipids and, consequently, of all biological membranes. The membrane fluidity, of crucial importance for its functioning, depends on its lipidic components. Phospholipids composed of chains of polyunsatured fatty acids increase the membrane fluidity because, by bending some chains, double bonds prevent them from compacting themselves perfectly. Membrane fluidity is also determined by the phospholipids/free cholesterol ratio, as cholesterol increases membrane viscosity. A diet based on a high proportion of essential polyunsatured fatty acids (fluid) would allow a higher incorporation of cholesterol (rigid) in the membranes to balance their fluidity, which would contribute to lower blood cholesterol levels. Brain membranes have a very high content in essential polyunsatured fatty acids for which they depend on alimentation. Any dietary lack of essential polyunsatured fatty acids has consequences on cerebral development, modifying the activity of enzymes of the cerebral membranes and decreasing efficiency in learning tasks. EPIDEMIOLOGICAL DATA: The prevalence of depression seems to increase continuously since the beginning of the century. Though different factors most probably contribute to this evolution, it has been suggested that it could be related to an evolution of alimentary patterns in the Western world, in which polyunsatured omega 3 fatty acids contained in fish, game and vegetables have been largely replaced by polyunsatured omega 6 fatty acids of cereal oils. Some epidemiological data support the hypothesis of a relation between lower depression and/or suicide rates and a higher consumption of fish. These data do not however prove a relation of causality. CHOLESTEROL AND DEPRESSION: Several cohort studies (on nondepressed subjects) have assessed the relationship between plasma cholesterol and depressive symptoms with contradictory results. Though some results found a significant relationship between a decrease of total cholesterol and high scores of depression, some other did not. Studies among patients suffering from major depression signalled more constantly an association between low cholesterol and major depression. Besides, some trials showed that clinical recovery may be associated with a significant increase of total cholesterol. CHOLESTEROL AND SUICIDAL BEHAVIOR: The hypothesis that a low cholesterol level may represent a suicidal risk factor was discovered accidentally following a series of epidemiological studies which revealed an increase of the suicidal risk among subjects with a low cholesterol level. Though some contradictory studies do exist, this relationship has been confirmed by several subsequent cohort studies. These findings have challenged the vast public health programs aimed at promoting the decrease of cholesterol, and even suggested to suspend the administration of lipid lowering drugs. Recent clinical studies on populations treated with lipid lowering drugs showed nevertheless a lack of significant increase of mortality, either by suicide or accident. In addition, several controlled studies among psychiatric patients revealed a decrease of the concentrations of plasma cholesterol among patients who had attempted suicide in comparison with other patients. POLYUNSATURATED FATTY ACID AND DEPRESSION: In major depression, all studies revealed a significant decrease of the polyunsaturated omega 3 fatty acids and/or an increase of the omega 6/omega 3 ratio in plasma and/or in the membranes of the red cells. In addition, two studies found a higher severity of depression when the level of polyunsaturated omega 3 fatty acids or the ratio omega 3/omega 6 was low. Parallel to these modifications, other biochemical perturbations have been reported in major depression, particularly an activation of the inflammatory response system, resulting in an increase of the pro-inflammatory cytokines (interleukins: IL-1b, IL-6 and interferon g) and eicosanoids (among others, prostaglandin E2) in the blood and the CSF of depressed patients. These substances cause a peroxidation and, consequently a catabolism of membrane phospholipids, among others those containing polyunsaturated fatty acids. The cytokines and eicosanoids derive from polyunsaturated fatty acids and have opposite physiological functions according to their omega 3 or omega 6 precursor. Arachidonic acid (omega 6) is, among others, precursor of pro-inflammatory prostaglandin E2 (PGE2), whereas polyunsaturated omega 3 fatty acids inhibit the formation of PGE2. It has been shown that a dietary increase of polyunsaturated omega 3 fatty acids reduced strongly the production of IL-1 beta, IL-2, IL-6 and TNF-alpha (tumor necrosis factor-alpha). In contrast, diets with a higher supply of linoleic acid (omega 6) increased significantly the production of pro-inflammatory cytokines, like TNF-alpha. Therefore, polyunsaturated omega 3 fatty acids could be associated at different levels in the pathophysiology of major depression, on the one hand through their role in the membrane fluidity which influences diverse steps of neurotransmission and, on the other hand, through their function as precursor of pro-inflammatory cytokines and eicosanoids disturbing neurotransmission. In addition, antidepressants could exhibit an immunoregulating effect by reducing the release of pro-inflammatory cytokines, by increasing the release of endogenous antagonists of pro-inflammatory cytokines like IL-10 and, finally, by acting like inhibitors of cyclo-oxygenase. THERAPEUTIC USE OF FATTY ACIDS: Data available concerning the administration of supplements of DHA (docosahexanoic acid) or other polyunsaturated fatty acids omega 3 are limited. In a double blind placebo-controlled study on 30 patients with bipolar disorder, the addition of polyunsaturated omega 3 fatty acids was associated with a longer period of remission. Moreover, nearly all the other prognosis measures were better in the omega 3 group. Very recently, a controlled trial showed the benefits of adding an omega 3 fatty acid, eicosopentanoic acid, among depressed patients. After 4 weeks, six of the 10 patients receiving the fatty acid were considered as responders in comparison with only one of the ten patients receiving placebo. CONCLUSIONS: Some epidemiological, experimental and clinical data favour the hypothesis that polyunsaturated fatty acids could play a role in the pathogenesis and/or the treatment of depression. More studies however are needed in order to better precise the actual implication of those biochemical factors among the various aspects of depressive illness.

Human requirement for N-3 polyunsaturated fatty acids.

AP Simopoulos — 2006-12-29T18:33:22-00:00

Poult Sci, Vol. 79, No. 7. (July 2000), pp. 961-970.

The diet of our ancestors was less dense in calories, being higher in fiber, rich in fruits, vegetables, lean meat, and fish. As a result, the diet was lower in total fat and saturated fat, but contained equal amounts of n-6 and n-3 essential fatty acids. Linoleic acid (LA) is the major n-6 fatty acid, and alpha-linolenic acid (ALA) is the major n-3 fatty acid. In the body, LA is metabolized to arachidonic acid (AA), and ALA is metabolized to eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The ratio of n-6 to n-3 essential fatty acids was 1 to 2:1 with higher levels of the longer-chain polyunsaturated fatty acids (PUFA), such as EPA, DHA, and AA, than today's diet. Today this ratio is about 10 to 1:20 to 25 to 1, indicating that Western diets are deficient in n-3 fatty acids compared with the diet on which humans evolved and their genetic patterns were established. The n-3 and n-6 EPA are not interconvertible in the human body and are important components of practically all cell membranes. The N-6 and n-3 fatty acids influence eicosanoid metabolism, gene expression, and intercellular cell-to-cell communication. The PUFA composition of cell membranes is, to a great extent, dependent on dietary intake. Therefore, appropriate amounts of dietary n-6 and n-3 fatty acids need to be considered in making dietary recommendations. These two classes of PUFA should be distinguished because they are metabolically and functionally distinct and have opposing physiological functions; their balance is important for homeostasis and normal development. Studies with nonhuman primates and human newborns indicate that DHA is essential for the normal functional development of the retina and brain, particularly in premature infants. A balanced n-6/n-3 ratio in the diet is essential for normal growth and development and should lead to decreases in cardiovascular disease and other chronic diseases and improve mental health. Although a recommended dietary allowance for essential fatty acids does not exist, an adequate intake (AI) has been estimated for n-6 and n-3 essential fatty acids by an international scientific working group. For Western societies, it will be necessary to decrease the intake of n-6 fatty acids and increase the intake of n-3 fatty acids. The food industry is already taking steps to return n-3 essential fatty acids to the food supply by enriching various foods with n-3 fatty acids. To obtain the recommended AI, it will be necessary to consider the issues involved in enriching the food supply with n-3 PUFA in terms of dosage, safety, and sources of n-3 fatty acids.

Omega-3 fatty acids in health and disease and in growth and development

Ap Simopoulos — 2006-12-29T16:11:05-00:00

Am J Clin Nutr, Vol. 54, No. 3. (1 September 1991), pp. 438-463.

Curry Consumption and Cognitive Function in the Elderly

Ng — 2006-10-24T18:47:13-00:00

American Journal of Epidemiology, Vol. 164, No. 9. (1 November 2006), pp. 898-906.

On the stability of the Earth's radiative energy balance: Response to the Mt. Pinatubo eruption

JE Harries — 2006-12-23T21:31:56-00:00

Geophysical Research Letters, Vol. 33 (15 December 2006), L23814.

Temporal decrease in upper atmospheric chlorine

L Froidevaux — 2006-12-23T21:29:56-00:00

Geophysical Research Letters, Vol. 33 (14 December 2006), L23812.

CTM study of changes in tropospheric hydroxyl distribution 1990–2001 and its impact on methane

Stig Dalsøren — 2006-12-23T21:28:09-00:00

Geophysical Research Letters, Vol. 33 (13 December 2006), L23811.

Was the 2003 European summer heat wave unusual in a global context?

Thomas Chase — 2006-12-23T21:15:57-00:00

Geophysical Research Letters, Vol. 33 (14 December 2006), L23709.

Bottom water warming along the pathway of lower circumpolar deep water in the Pacific Ocean

Takeshi Kawano — 2006-12-23T21:13:56-00:00

Geophysical Research Letters, Vol. 33 (14 December 2006), L23613.

Calculated and observed climate change in the thermosphere, and a prediction for solar cycle 24

Liying Qian — 2006-12-23T18:42:54-00:00

Geophysical Research Letters, Vol. 33 (6 December 2006), L23705.

Effect of climate and CO2 changes on the greening of the Northern Hemisphere over the past two decades

Shilong Piao — 2006-12-23T18:39:21-00:00

Geophysical Research Letters, Vol. 33 (9 December 2006), L23402.

An increasing CO2 sink in the Arctic Ocean due to sea-ice loss

Nicholas Bates — 2006-12-23T18:37:46-00:00

Geophysical Research Letters, Vol. 33 (9 December 2006), L23609.

Impact of clouds on radiative heating rates in the tropical lower stratosphere

S Fueglistaler — 2006-12-23T18:24:33-00:00

Journal of Geophysical Research, Vol. 111 (5 December 2006), D23202.

Anomaly of heat content in the northern Atlantic in the last 7 years: Is the ocean warming or cooling?

VO Ivchenko — 2006-12-19T11:17:00-00:00

Geophysical Research Letters, Vol. 33 (25 November 2006), L22606.

Metabolism of [alpha]-linolenic acid in humans

GC Burdge — 2006-12-12T21:41:22-00:00

Prostaglandins, Leukotrienes and Essential Fatty Acids, Vol. 75, No. 3. (September 2006), pp. 161-168.

[alpha]-Linolenic acid (18:3n-3) is essential in the human diet, probably because it is the substrate for the synthesis of longer-chain, more unsaturated n-3 fatty acids eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3) which are required for tissue function. This article reviews the recent literature on 18:3n-3 metabolism in humans, including fatty acid [beta]-oxidation, recycling of carbon by fatty acid synthesis de novo and conversion to longer-chain polyunsaturated fatty acids (PUFA). In men, stable isotope tracer studies and studies in which volunteers increased their consumption of 18:3n-3 show conversion to 20:5n-3 and 22:5n-3, but limited conversion to 22:6n-3. However, conversion to 18:3n-3 to 20:5n-3 and 22:6n-3 is greater in women compared to men, due possibly to a regulatory effect of oestrogen, while partitioning of 18:3n-3 towards [beta]-oxidation and carbon recycling was lower than in men. These gender differences may be an important consideration in making dietary recommendations for n-3 PUFA intake.

Compartmental modeling to quantify alpha-linolenic acid conversion after longer term intake of multiple tracer boluses

Petra Goyens — 2006-12-12T21:28:31-00:00

J. Lipid Res., Vol. 46, No. 7. (1 July 2005), pp. 1474-1483.

To estimate in vivo alpha-linolenic acid (ALA; C18:3n-3) conversion, 29 healthy subjects consumed for 28 days a diet providing 7% of energy from linoleic acid (C18:2n-6) and 0.4% from ALA. On day 19, subjects received a single bolus of 30 mg of uniformly labeled [13C]ALA and for the next 8 days 10 mg twice daily. Fasting plasma phospholipid concentrations of 12C- and 13C-labeled ALA, eicosapentaenoic acid (EPA; C20:5n-3), docosapentaenoic acid (DPA; C22:5n-3), and docosahexaenoic acid (DHA; C22:6n-3) were determined on days 19, 21, 23, 26, 27, and 28. To estimate hepatic conversion of n-3 fatty acids, a tracer model was developed based on the averaged 13C data of the participants. A similar tracee model was solved using the averaged 12C values, the kinetic parameters derived from the tracer model, and mean ALA consumption. ALA incorporation into plasma phospholipids was estimated by solving both models simultaneously. It was found that nearly 7% of dietary ALA was incorporated into plasma phospholipids. From this pool, 99.8% was converted into EPA and 1% was converted into DPA and subsequently into DHA. The limited incorporation of dietary ALA into the hepatic phospholipid pool contributes to the low hepatic conversion of ALA into EPA. A low conversion of ALA-derived EPA into DPA might be an additional obstacle for DHA synthesis. 10.1194/jlr.M400514-JLR200

Miocene evolution of atmospheric carbon dioxide

Mark Pagani — 2006-12-10T13:02:38-00:00

Paleoceanography, Vol. 14, No. 3. (1999), pp. 273-292.

Atmospheric carbon dioxide concentrations over the past 60 million years

Paul Pearson — 2006-12-10T12:54:41-00:00

Nature, Vol. 406, No. 6797. (2000), pp. 695-699.

Long-term motor cortex plasticity induced by an electronic neural implant

Andrew Jackson — 2006-10-25T21:40:07-00:00

Nature (22 October 2006)

On global forces of nature driving the Earth's climate. Are humans involved?

LF Khilyuk — 2006-12-08T16:47:48-00:00

Environmental Geology, Vol. V50, No. 6. (2006), pp. 899-910.

Isotopic Evidence for Dietary Variability in the Early Hominin Paranthropus robustus

Matt Sponheimer — 2006-12-07T21:19:43-00:00

Science, Vol. 314, No. 5801. (10 November 2006), pp. 980-982.

Traditional methods of dietary reconstruction do not allow the investigation of dietary variability within the lifetimes of individual hominins. However, laser ablation stable isotope analysis reveals that the delta13C values of Paranthropus robustus individuals often changed seasonally and interannually. These data suggest that Paranthropus was not a dietary specialist and that by about 1.8 million years ago, savanna-based foods such as grasses or sedges or animals eating these foods made up an important but highly variable part of its diet.

Climate change: The south–north connection

Eric Steig — 2006-11-09T05:19:12-00:00

Nature, Vol. 444, No. 7116., pp. 152-153.